As a fuel cell, a constitution is suggested in which collector plates, insulating plates and end plates are laminated on opposite sides of a stack (a laminate) constituted of a plurality of layers of cells (unitary cells) each formed by holding a membrane-electrode assembly between plate-like separators on the opposite sides. In such a fuel cell, when a fuel gas and an oxidizing gas are supplied from the outside to the membrane-electrode assemblies of the cells, a power is generated in the cells owing to an electrochemical reaction to discharge a surplus gas, a water vapor, produced water and the like from the cells. Furthermore, a heat medium such as cooling water is supplied and discharged between the cells.
A plate member such as the separator, the collector plate, the insulating plate and the end plate constituting the fuel cell is provided with manifolds for supplying and discharging fluids so that the manifolds extend through the members along a laminating direction. Fluids such as a gas and cooling water are supplied and discharged via the manifolds. Both front and back surfaces of the separators are provided with a large number of channels crossing the laminating direction at right angles, in addition to through holes for the manifolds. The channel of the separator provided on a cell inner side is a channel to supply or discharge the fuel gas and the oxidizing gas to or from the membrane-electrode assembly, and the channel of the separator provided on a cell outer side is a channel to supply or discharge a heat medium such as the cooling water between the adjacent cells.
A plate member such as the separator and the end plate is constituted of a metal material such as stainless steel or a composite material such as FRP in which deterioration such as corrosion is not easily generated, even when the material comes in contact with the fluid. When the plate member is brought into direct contact with fluids such as the fuel gas, the oxidizing gas and the heat medium for a long period, deterioration such as the corrosion occurs. Therefore, at present, a technology to cover a contact portion between each member and each fluid with a resin coating film has been suggested. Furthermore, in recent years, a technology to cover inner wall surfaces of the through holes for the manifolds with gaskets is suggested (e.g., see Japanese Patent Application Laid-Open No. 2005-108524).